Hello gents,

I'm having a no sprk issue and just threw my test light on. Clipped to pos of battery and touching the neg (tach test) pole on the coil.

As soon as I touch the coil I get a solid faint glow. No blinking. When I jump the solenoid the glow stays solid but become very faint.

I'm a boner with this and am not sure what this even means?

What to replace first...

 

If the light doesn't blink, then the ignition module is not firing the coil. This could happen because the ignition module is not receiving power, the ignition module is bad, the distributor pickup is bad, or there is a wiring issue.

Jumping at the solenoid won't work; for this test you need to crank with the key, or at least keep the key in RUN so that the ignition circuit has power.

 

Thanks, fmc.

I did replace the module and then tried the test light two different ways:

first: light clipped to battery pos and pointer touched to the tach test pole of the coil. That was the really faint glow.

second: test light clipped to the tach test on the coil and the pointer touching a ground spot. This one the test light was BRIGHT when the key was on run but no flicker at all.

I figure the next move is to replace the magnet pick-up in the dizz.

I will also need to learn how to use a multimeter and figure out how to test if the module is getting power.

 

The second method was the correct way to do this.
The test light should flash while the starter is cranking it over.

 

Also check the grounding screw under the dist cap, it looks like a hold down clamp were the wire harness changes from 3 to 2 wires.
I agree... it is time to get out the volt meter.
Jim

 

With KEY ON and the test light connected it WON'T blink unless the engine is running.

You'll need to connect the light to COIL - and to GROUND and hit KEY START and watch for "blinking"

Josh

 

Just a side note on the test light connectivity. You actually will see the blinking action with both configurations (TACH TEST to battery positive, or TACH TEST to ground). This is because the TACH TEST terminal (coil negative) is either pulled down to ground, or left open-circuit. I confirmed both on my '79.

In the first method (TACH TEST to battery positive), when the coil is pulled to ground by the module, the light turns ON since it's hot on the other side. When the module open-circuits the coil to fire the plug, the light sees 12 volts on both sides (battery on one side, and upstream of coil primary winding on the other side). No current flows through the light so it turns OFF. The light blinks as the coil is pulled to ground and then forced open, over and over.

In the second method (TACH TEST to ground), when the coil is pulled to ground by the module, the light turns OFF because it has ground on one side, and ground on the other side, through the power transistor in the module. When the module forces the coil open-circuit, the light turns ON because it has ground on one side, and 12 volts on the other side, upstream of the coil primary winding. Again, the light blinks as the coil is pulled to ground and then forced open, over and over.

While I found that both work as expected, I'd recommend to stick with the second method (TACH TEST to ground) as Jim and Josh recommend, because that's what is listed in all the diagnostics books. It's a lot safer to do it this way, because if you're doing the first method (TACH TEST to battery positive), it's very easy for the test light to come apart and leave you with a hot-at-all-times wire dangling off your battery. Also, there may be some other effect with the first method that could damage the module or affect the brightness that I'm not thinking of right now. For example, when you use the second (correct) method, the light sees full battery voltage when it is ON, so the blinking action is very easy to see. With the first method, when the light is ON, its brightness will be affected by any collector-path resistance in the ignition module. In that case, the blinking action could be faint and difficult to see.

 

I just got back from a week back east and am still stymied. I have replaced the ignition module and the distributor. I did find a loose wire in the plug connecting the distributor- the all black wire. It seems that has been partially pulled out of the back of the plug.



After being told by my local NAPA that there is no available replacement plug and that I will need to make one to connect to the dizz I snipped the pulled wire and ran a jumper which I wound around the matching terminal on the male plug connected to the dizz.

I just switched the key to ON and went at it with the test light. This is what I found:

With the test light clipped to the positive terminal on the battery I get a bright solid light when I touch the frame and when I touch the all black wire at the dizz plug (this is the wire partially pulled loose from the plug). I get a blinking light when I touch the test light to the "L" shaped ground plugs that connect to the intake and to the old oil pressure sensing unit. These guys:



When I clip the test light to the battery NEGATIVE battery terminal I get a solid bright light when I touch the test light to the positive terminal at the coil AND the negative terminal of the coil. I get a blinking light at the "L" plugs.

When I move the test light and clip it to the negative coil (tach test) I get a solid bright light when I touch the test light to the frame and when I touch the pulled wire at the dizz. Once again, blinking light when I touch the test light to the "L" plugs.

I pulled plug #1 and verified that there is no spark.

I'm at a loss about where I am losing my ground or power. The only thing I haven't replaced are the coil or the plug wires (which are fairly new).

Any educated suggestions would be greatly appreciated. And, remember, I'm a bit of a dummy. I want to follow your advice so it would best keep to the small words and basic steps.

 

Use your test light to see if the red wire (2 wire plug) going into the DS2 module has power with the key ON. If the IGN module is not getting power it will cause your problem.

Leave the "L" connectors allow, the are not part of the IGN system.
Jim

 

With the ignition on "run" I checked the two-wire plug at the module. The pair coming out of the module are red/white but the matching pair coming from my truck are light blue/red. Odd. Maybe. The light blue wire from the truck is the mate for the red going into the module.

With the test light clipped to ground I touched the point into the blue wire plug and it glowed bright and solid.

From what I gather that should mean power into the module. Right?

 

... CORRECT

What brand name DS2 module do you have?
Most DS2 modules conduct current with the key ON... some after market ones don't... this makes it hard to trouble shoot this stuff online.
It would seem based on your info that your module in not conducting any current with the key ON.
It would help if you used a Voltmeter to take some measurements.
Jim

 

The module is branded NAPA/ Echlin. It was the heavy-duty option.

I just got back from the auto store with a multimeter, where, interestingly, I parked right next to a Ferrari GT California.

I can get out there in a bit and see what the meter reads at the two-wire module plug as well as other spots around the coil.

Ugh. Electrical... I' m just learning the mechanicals of this rig. Electrical issues just kill me.

 

The Napa TP-40 DS2 IGN module does conduct current with the Key ON. This is a high dollar module and a good choice.

Do all voltage testing with the key ON, the voltage at the coil POS should be 7-8 volts due to the resistor wire. If it is 12 volts the DS2 module is not turning ON which means it is not getting power to it or it is a BAD MODULE. I know you tested the power to the module and it was good... so I am at a loss here. At this point I would just take KEY ON voltage reading every where and post the numbers here.
Good Luck
I am leaving Seatac and heading over the pass this morning... it is raining outside and snowing up on the Pass...

Jim

 

I am as confused as ever, but here are the readings. When checking power at the plug leading into the module I used the positive lead in the plug and grounded the negative lead to the frame. For all other measurements I placed the positive lead on the positive battery terminal and used the negative lead to test different points. I have my multimeter set to 20v DC. The "power at dizz wire" reading was taken at the jumper going around the broken wire from the dizz plug (see earlier post about the wire pulled from the dizz plug).

With the key set to RUN (clicked far right/clockwise):
power at module: 12.3
+ on the coil: .05
- on the coil: .05
- on dizz wire: 12.4

With key set to OFF (straight up):
power at module: 0.00
+ on the coil: 12.7
- on the coil: 12.7
- on dizz wire: 12.7

With key REMOVED:
power at the module 0.00
+ on the coil: 12.74
- on the coil: 12.74
- on dizz wire: 12.74

With key set to AUXILLARY (far left):
power at the module: 0.00
+ on the coil: 12.72
- on the coil: 12.72
- on dizz wire: 12.72

I checked these with the old module as well and got very much the same readings.

I am a bit stumped at the .05V readings on both the positive and negative coil poles with the key set to run. I understand that it should be around 7 on the coil pos (because of resistance) and 12 on the negative (tach test). Or not?

 

Okay. I am a moron.

That said... It's amazing how different the ignition system works once you figure out that you need to reconnect the green wire to the negative pole of the coil.

Go ahead and laugh (at) with me.

To clarfy: this whole damn time I've been dunking around while not having the coil grounded. Once I traced wires for a while and connected the green to thr tach test pole I got proper voltage readings and spark.

Durrrr....